How do you complete the square to answer quadratic equations?
x2+6x-2 = 0
We use completing the square when the equation cannot be factorised. Begin by placing x2 in the brackets and halving the number in front of the x (also known as the coefficient of x) to form (x+3)2 . Now if we expanded the brackets and we would have x2 +6x+9. Since +9 is not part of the original equation we must subtract it giving (x+3) 2 -9. Returning to the original equation we must also -2 giving us (x+3)2-11.
x2+6x-2 = (x+3)2 -11 = 0 so to solve, we treat like a normal equation.
(x+3)2 = 11
(x+3) = √(11)
x=-3+/-√(11)
MM
Related Maths GCSE answers
All answers ▸A ladder 5.5m long is leaning against a wall. the foot of the ladder is 1.7m away from the wall. how far up the wall does the ladder reach?
Solve: x^2-x-6 using factorisation.
The perimeter of an isosceles triangle is 16cm. The length of the base of the triangle is x+4 and that of the other two sides is x+3. Find the area of the triangle
What is the size of the interior angle of a regular 12-sided polygon?